In the display field, a precise modulation of light is always required. The modulation includes, but not limited to, a propagation direction, an amplitude, a phase and a polarization. The amplitude (or the light intensity) can be modulated by the combination of a liquid crystal and a polarizer. The polarization can generally be modulated by a half-wave plate or a quarter-wave plate. The phase can generally be modulated by controlling an optical path difference by a spatial light modulator.
Currently, a Liquid Crystal on Silicon (LCoS) spatial light modulator (LCoS-SLM for short) is generally used to modulate the phase. Like ordinary liquid crystal displays, the principle of LCoS-SLM is to rely on the modulation by liquid crystal molecules to the phase of light, so that the rotational speed of the liquid crystal molecules determines the response time of the LCoS-SLM. The rotational speed of the liquid crystal molecules is slow, and hence LCoS-SLM always has a long response time.